Rapping exhaust

adileo

adileo

Well-known member
Hi guys

When I 1st bought the 52 F1 (all stock v8), it use to rap / backfire through the exhaust, when backing off on gas. I did a tune up about 3 months ago, adjusted timing and it stopped. At the same time I installed a new carb. Tonight it started again, only when coming off the gas. When at idle it seems like the idle is too slow.

Now I have (I am guessing) two options:
1) check timing
2) turn carb idle screw up.

Which would you go for first?
 
Timing affects the idle speed, but idle speed should be correct to time correctly. You might have to re-adjust idle after timing. IMHO
 
40 Deluxe said:
If you were a teenager in the fifties, you lived for that backfire sound. Don't be an old fogie!
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That's what I was thinking! I had a big engine mustang with very short pipes that would back down and shoot fire out of both sides under the doors. Boy did I think that was cool.
 
Mike51Merc said:
Rapping (or popping) on deceleration indicates a lean condition. Adjust idle mixture richer.
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2X Mike51. After I installed my Bubba distributor, I had the same experience because finally it was timed properly. Adjusted the idle screws, and that was the end of the "popping" on deceleration.

Dick.
 
JSeery said:
That's what I was thinking! I had a big engine mustang with very short pipes that would back down and shoot fire out of both sides under the doors. Boy did I think that was cool.
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i had a 350 chebby that would do the same thing i'm 51 and i still think its kool!
 
its just part of real motoring the 3 'Cs' [cams carbs compression] or as we say here NBC [no blo''' computers ] so embrace and enjoy
 
Checked points, rotor and distro cap all looked good. Pulled plugs and they all looked a lil sooty. Cleaned, re-gapped and installed. Adjusted fuel mixture and idle is now nice smooth and truck starts and a quick hit of button.

Took for ride was still backfiring out exhaust when de-acceleration. Shut truck off did couple errands and now it’s not backfiring on de-acceleration.

Could it be condenser going bad? Could it be Electical?
 
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Andy, this is a long shot-are the carburetor mounting nuts snug? Sometimes a small vacuum leak will cause a backfire. May want to hook up a vacuum gauge and see what the readings are.
 
Steve

Thanks. I just checked and the back carb nut took a qtr turn. I’ll drive it this week and see if this inconsistent back fire returns.
 
I think that I've been on Face Book to much lately...I kept looking for the "like" button on a lot of those comments. Ha Ha....I love the sound of my Flatty rapping too. going to be even better when I'm able to switch over to straight pipes!
Randy
 
That back carb nut being a lil loose may have been it. Took truck out few times no popping on deacceleration. Thanks Steve and rest!
 
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